Castable metallic illuminant fuel containing nitrocellulose plasticized binder

ABSTRACT

A castable illuminant containing a particulate mixture of fuel and oxidizer held together by an energetic plastisol type binder. A process of preparing devices containing the aforesaid composition wherein such ingredients are distributed into a viscous mass, poured directly into an end-item container, and thermally cured in a state ready for use as an illuminating device.

Unite States Patent Swotinsky et a1.

1 1 Feb. 6, 1973 3,152,935 10/1964 Cadwallader 149/19 3,364,086 1/1968 Oversohl et a1 ..149/19 X 3,375,148 3/1968 Finnegan et al. 149/18 3,507,114 4/1970 Webb ....l49/l9 3,551,224 12/1970 Huskins et al.. ....149/18 3,554,820 1/1971 Evans ..149/19 FOREIGN PATENTS OR APPLICATIONS 48,163 6/1930 Norway 149/65 Primary Examiner- Carl D. Quarforth Assistant ExaminerP. A. Nelson Attorney--Harry M. Saragovitz, Edward J. Kelly and Herbert Bell [57] ABSTRACT A castable illuminant containing a particulate mixture of fuel and oxidizer held together by an energetic plastisol type binder.

A process of preparing devices containing the aforesaid composition wherein such ingredients are distributed into a viscous mass, poured directly into an end-item container, and thermally cured in a state ready for use as an illuminating device.

6 Claims, N0 Drawings CASTABLE METALLIC ILLUMINANT FUEL CONTAINING NITROCELLULOSE PLASTICIZED BINDER The invention described herein may be manufactured, used and licensed by or for the Government for Governmental purposes without the payment to us of any royalties thereon.

This invention relates to a castable illuminant of a pyrotechnic nature and a method of making the same.

More particularly, this invention relates to a pyrotechnic device having a castable charge of improved composition and a method of making the same.

In many cases, pyrotechnic devices are utilized for the production of light by both the private sector and the military. The military require such devices for support of troops during engagements at night. The latter needs relative to the number of devices required are of a continuing nature and are especially acute during periods of hostility. However, such use by the military has placed stringent conditions on the characteristics and effectiveness of such devices above and beyond that which is required by all other users. In effect, what is required is a device of a pyrotechnic nature which produces light of a maximum intensity for the longest possible time. In addition, due to the enormous nature in the number of devices that may be needed, each item must be able to be procured at the least possible cost. However, in the past, the inherent difficulties encountered in the conventional method of processing a pyrotechnic device such as a flare have limited, among other things, the efficiency of its light-producing function and the attainment of optimum effectiveness as a device for military use.

In the art, the conventional method of producing devices of a pyrotechnic nature encompasses the feeding of the loose granular ingredients to a suitable container, in incremental stages, followed in sequence by the compaction of the individual layers of particulate material by mechanical presses in order to achieve the desired density in the final product. The latter, in general, being a light-producing device of the stick or candle variety having the shape of a right cylindrical column-type case possessing relatively thin walls within which is housed the pyrotechnic mixture. Generally, a relatively small amount of binder is added to the granular mass during processing in order to hold the particles together and to impart a measure of strength to the column. I

One of the difficulties, inherent in the aforesaid conventional procedure for the manufacture V of pyrotechnic devices such as flares, centers around the compaction presses use during processing. The availability of the industrial presses described is such that the production capacity of the flares is limited and this is of utmost importance during times of national emergency.

A further difficulty lies in the size of the flare that can be manufactured by such procedures utilizing available industrial equipment. In many cases, the size of the flare determines the duration ofits useful life as a light-producing source. However, in the past, the largest flare that had been manufactured possessed a maximum diameter of only twelve inches.

A still further difficulty of the conventional procedure lies in the limitation of the variety of configurations that may be produced by available industrial equipment. For instance, in the past, the presses utilized by industry for compaction have been of the hydraulic piston-type variety and this alone has limited the configuration of the flares to that of a right circular cylinder. This latter limitation alone has diminished the overall effectiveness of the product as a device for military support.

Another difficulty lies with the use of the conventional binder during processing for strength and cohesiveness of the granular column. The strength of the pyrotechnic charge has always been a compromise with the efficiency of the illuminating function of the device. The least amount of binder has always resulted in a diminishment of the light produced by the charge of the device.

For instance, an inert binder such as carboxyl terminated polybutadiene elastomer was utilized as the cohesive element of a pyrotechnic composition. However, experience has shown that compositions containing such inert binders were far below acceptable stan dards in regard to light intensity and color. The inert binder was found to partially obscure the white light emitted by the particulate mixture of fuel and oxidizer with the net result of an emission of a less efficient yellow tinted light.

The subject invention answers the aforesaid needs of the art with special emphasis on the production of an effective illuminating source of a pyrotechnic nature having optimum efficiency in the generation oflight for a relatively long duration of time, such production being carried out without encountering the difficulties of the art as heretofore described.

It is therefore an object of this invention to provide an illuminating source of improved composition and a method of making the same.

Another object is to provide a castable pyrotechnic of improved composition and a method of making the same.

A further object is to provide a light-producing device of a pyrotechnic nature having a castable charge and a method ofmaking the same.

A still further object is to provide an improved method of producing a pyrotechnic device, such method having facile use under a wide variety of service conditions.

Other objects and many of the attendant advantages of this invention will become better understood upon a reading of the following detailed description.

Broadly, the improved composition of the subject invention comprises a pyrotechnic charge consisting essentially of a particulate mixture of fuel and oxidizer held together by an energetic plastisol-type binder.

The composition of this invention is inherently based on the discovery that a high energy plastisol-type binder would not deteriorate the light emission of such composition but, would rather enhance the light produced by the burning fuel and oxidizer, since the binder is of itself highly combustible. The binders utilized in this composition are of the nitrocellulose type plasticized with nitrate esters. It was found that although a significantly lower level of active solids was utilized in this pyrotechnic system, the energetic binder contributed significant light and total light output was maintained equivalent to that of a standard flare composition. As a result of this discovery, it has been found possible to manufacture pyrotechnic compositions containing fuel and oxidizer in concentrations as low as 65 per cent by weight using such an energetic binder, which are equivalent in light efflciency to a standard flare composition.

In the preferred embodiment, the composition of this invention encompasses the following ingredients in the ranges specified.

a. 25 to 50 per cent metallic fuel;

b. 15 to 35 per cent oxidizer;

c. to per cent nitrocellulose;

d. 10 to 40 per cent of a nitrate ester type plasticizer;

e. 0 to 2 per cent stabilizer; and

f. 0 to 2 per cent crosslinking agent.

Conventional fuels and oxidizers may be used in the aforesaidcomposition with the added advantage that an illumination equivalent to the standard sources may be obtained, even through the solids concentration of active ingredients in the present composition are drastically less than that required for such standard sources. Illustrative metallic fuels which can be utilized are of the magnesium and aluminum variety, while the oxidizers can include such materials as sodium and potassium nitrate.

The energetic plastisol-type binder, as noted, was of the nitrocellulose type plasticized with a nitrate ester and cross-linked with tolylene diisocyanate. The nitrate esters which have proved themselves of acceptable behavior in the present composition included nitroglycerin, triethylene glycol dinitrate and butane triol trinitrate. As heretofore stated, this binder does not deteriorate the light emission of the composition but, indeed, enhances the light produced by the burning fuel and oxidizer as a result of its combustible nature.

In addition, materials such as 2-nitro-diphenylamine and ethyl centralite may be added to stabilize the composition.

An illuminating source which performed in a highly satisfactory manner in the field had the following composition.

Ingredient by Weight Magnesium 39.00 Sodium Nitrate 26.00 Nitrocellulose (12.6% Nitrogen) 6.82 Nitroglycerin 0.10 Triethylene Glycol Dinitrate 18.09 Butane Triol Trinitrate 9.46 2-Nitrodiphenylamine 0.28 Tolylene Diisocyanate 0.25

TABLEI Standard Cast No. 1 Cast No. 2

Type of Case Cardboard Cardboard Plastic No. of Tests 5 5 13 Charge Weight, gm 150.0 209.1 204.8 Charge Height, in 3.8 5.9 58 Density, gm/cc 1.81 1.70 1.70 Average Candlepower, 10 91.3 41.0 1 14.9 Burning Time, sec 50.2 151.0 74.7 Burning Rate, in/min 4.5 2.4 4.7 Candlepower-Seconds, 10 45.9 60.9 84.9 Candlepower/sq.in., 10 68.6 30.7 86.3 Efficiency, C-sec/gm, 10 30.8 29.1 41.4 Efficiency, C-sec/cc, 10 55.4 49.5 70.5

As is evident from the above summarized results, the charges cast in cardboard had a slower rate'of burning when compared to that of the standard charge. However, the luminous efficiency of both were substantially 7 equivalent. In the case of the charges cast in plastic tubes, the results indicated that these had a faster burning rate than the specimens cast in cardboard. This was probably due to extensive side burning of the illuminant contained in the plastic containers. In any case, it is self-evident that excellent luminous efficiency was achieved by the latter flare.

Thus, it can be seen from the aforesaid that we have developed a family of low-cost, castable illuminants of a pyrotechnic nature which may be utilized to provide intensity of illumination substantially equivalent to that of a standard source for a comparable duration of time. In the past, it was very difficult to vary the burning rate and illuminous efficiency of a specific standard source. Now, however, this may be accomplished in a simple manner by varying the total concentration and particle size of the individual solids in the cast charge as well as the type and relationship of all the ingredients to each other including the energetic binder, fuel and oxidizer.

The process of the present invention, which was utilized to prepare the aforesaid composition, broadly encompasses a procedure wherein a conventional fuel and oxidizer are combined with an energetic binder of the plastisol-type in the form of a mass which is subsequently shaped and cured in a state ready for packaging.

More specifically, in the preferred embodiment, this invention encompasses a procedure where the aforesaid ingredients are distributed into a viscous mass, which is then poured directly into the end-item container and thermally cured in a state ready for use. The distribution may be carried out by conventional methods of mixing under a vacuum, however, the casting is always carried out under a vacuum. In this manner, it is possible to manufacture castable illuminant compositions containing any combination of metallic fuels and oxidizers in concentrations as low as 65 per cent by weight utilizing an energetic material as binder.

Initially, in the production of the blended fluid mass, the energetic binder is first added to the mixing kettle under agitation, the liquid portion thereof being essentially in the dehydrated state while the solid portion is essentially oven dried. The dehydration of the liquid portion can be accomplished by passing dry air through the fluid until it is essentially water free. In the case of the preferred embodiment, the air was passed through the liquid portion, which consisted of about 65 per cent triethylene glycol dinitrate and 35 per cent butane triol trinitrate, for approximately 72 hours. The solvent portion was then found to have a moisture of less than about 0. l 4 per cent. The solid portion of the binder was also prepared by drying in an oven for 24 hours at 60 C. The mixing stage was continued under vacuum to produce a fluid and cohesive mass before any further addition was made and this required an interval of about 30 minutes.

Subsequently, a dried fuel of the metallic variety such as magnesium was added to the kettle and agitation was continued until the metallic fuel was evenly dispersed which required about minutes of mixing time. Prior to being added to the kettle, the magnesium is preferably dried for the same period of time as the solid portion of the binder.

At this stage of processing, to insure an even distributionof the oxidizer throughout the mass of fuel and binder, the oxidizer was added in incremental stages to the mass while it is being continuously blended in the operating mixer. A schedule which proved quite satisfactory was to add the oxidizer such as sodium nitrate in three equal increments with a distribution time of minutes between increments and 30 minutes after the final addition of the oxidizer to the mix. Prior to the addition of the oxidizer, it was heated at 60 C. for 24 hours to insure its dryness.

After all the aforesaid ingredients of the mass are wet and evenly distributed, the temperature of the system was raised to about 105 F. and mixing was continued. This thermal treatment was continued for 1 hour, however, after 45 minutes tolylene diisocyanate was added to the mass. The latter material is used to crosslink the nitrocellulose in order to improve the binding action of the binder.

Subsequent to the aforesaid processing, when the mass had attained a pourable viscosity, the mass was cast into suitable containers, such as dry cardboard tubes, under a vacuum of 5 inches of mercury. To insure the dryness of the containers, they were heated in an oven for 24 hours at 60 C.

At this stage, the receptacles containing the cast charges were cured in an oven at 60 C. for a period of between 3 and 5 days, after which the illuminant devices were ready for use.

As is evident from the aforesaid, the process of the present invention was used to manufacture pyrotechnic illuminants by a simple mixing, casting and curing.

Some of the advantages of this process include the production of a pyrotechnic having an energetic binder which permits the achievement, in use, of luminous efficiency equivalent to those of conventional charges and this is achieved with a reduction in the amount of active solid ingredients required by the process. For instance, the product of this process requires as little as 65 per cent solids concentration of fuel and oxidizer as compared to the per cent concentration required of conventional products produced by conventional procedures. Another advantage pertains to the size and configuration of the charge produced by the present process, there are no limitations as to either characteristic as there have been in the past with conventional procedures and, in some cases, significant loading densities are also achieved. The process further permits the forming of a full-length charge in one casting operation whereas, in the past, several operations were required to achieve the same result.

What is claimed is: l. A castable pyrotechnic illuminant consisting essentially of at least 65 per cent by weight a particulate mixture of metallic fuel and oxidizer held together by an energetic plastisol binder consisting essentially of nitrocellulose plasticized with a nitrate ester.

2. The castable illuminant of claim 1 containing at least about 65 per cent by weight of said particulate mixture.

3. The castable illuminant of claim 1 consisting essentially of:

a. about 25 to 50 per cent metallic fuel,

about 15 to 35 per cent oxidizer, about 5 to 15 per cent nitrocellulose,

about 10 to 40 per cent nitrate ester type plasticizer, about up to 2 per cent stabilizer, and

f. about up to 2 per cent tolylene diisocyanate, all

percentages being by weight.

4. The castable illuminant of claim 3 wherein said nitrate ester type plasticizer is selected from the group consisting of nitroglycerin, triethylene glycol dinitrate, and butane triol trinitrate.

5. The castable illuminant of claim 3 consisting essentially of:

a. about 39 per cent magnesium,

b. about 26 per cent sodium nitrate,

c. about 6.82 per cent nitrocellulose containing about 12 per cent nitrogen,

d. about 0. 10 per cent nitroglycerin,

e. about 18.09 per cent triethylene glycol dinitrate f. about 0.46 per cent butane triol trinitrate,

g. about 0.28 per cent 2-nitrodiphenylamine, and

h. about 0.25 per cent tolylene diisocyanate.

6. The castable pyrotechnic illuminant of claim 1, wherein the metallic fuel is selected from the group consisting of magnesium and aluminum. 

1. A castable pyrotechnic illuminant consisting essentially of at least 65 per cent by weight a particulate mixture of metallic fuel and oxidizer held together by an energetic plastisol binder consisting essentially of nitrocellulose plasticized with a nitrate ester.
 2. The castable illuminant of claim 1 containing at least about 65 per cent by weight of said particulate mixture.
 3. The castable illuminant of claim 1 consisting essentially of: a. about 25 to 50 per cent metallic fuel, b. about 15 to 35 per cent oxidizer, c. about 5 to 15 per cent nitrocellulose, d. about 10 to 40 per cent nitrate ester type plasticizer, e. about up to 2 per cent stabilizer, and f. about up to 2 per cent tolylene diisocyanate, all percentages being by weight.
 4. The castable illuminant of claim 3 wherein said nitrate ester type plasticizer is selected from the group consisting of nitroglycerin, triethylene glycol dinitrate, and butane triol trinitrate.
 5. The castable illuminant of claim 3 consisting essentially of: a. about 39 per cent magnesium, b. about 26 per cent sodium nitrate, c. about 6.82 per cent nitrocellulose containing about 12 per cent nitrogen, d. about 0.10 per cent nitroglycerin, e. about 18.09 per cent triethylene glycol dinitrate f. about 0.46 per cent butane triol trinitrate, g. about 0.28 per cent 2-nitrodiphenylamine, and h. about 0.25 per cent tolylene diisocyanate. 